Automated IT Service Fault Diagnosis Based on Event Correlation Techniques

In the previous years a paradigm shift in the area of IT service management could be witnessed. IT management does not only deal with the network, end systems, or applications anymore, but is more and more concerned with IT services. This is caused by the need of organizations to monitor the efficiency of internal IT departments and to have the possibility to subscribe IT services from external providers. This trend has raised new challenges in the area of IT service management, especially with respect to service level agreements laying down the quality of service to be guaranteed by a service provider. Fault management is also facing new challenges which are related to ensuring the compliance to these service level agreements. For example, a high utilization of network links in the infrastructure can imply a delay increase in the delivery of services with respect to agreed time constraints. Such relationships have to be detected and treated in a service-oriented fault diagnosis which therefore does not deal with faults in a narrow sense, but with service quality degradations. This thesis aims at providing a concept for service fault diagnosis which is an important part of IT service fault management. At first, a motivation of the need of further examinations regarding this issue is given which is based on the analysis of services offered by a large IT service provider. A generalization of the scenario forms the basis for the specification of requirements which are used for a review of related research work and commercial products. Even though some solutions for particular challenges have already been provided, a general approach for service fault diagnosis is still missing. For addressing this issue, a framework is presented in the main part of this thesis using an event correlation component as its central part. Event correlation techniques which have been successfully applied to fault management in the area of network and systems management are adapted and extended accordingly. Guidelines for the application of the framework to a given scenario are provided afterwards. For showing their feasibility in a real world scenario, they are used for both example services referenced earlier

Experimental dataset on electrolyte mixtures containing fluoroethylene carbonate and lithium bis(trifluoromethanesulfonyl)imide

These data and analyses support the research article “Low-flammable electrolytes with fluoroethylene carbonate based solvent mixtures and lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) for lithium-ion batteries” [1]. The data and analyses presented here include fitted data for density measurements, temperature dependence of density and specific volume of the mixtures, detailed viscosity measurements and conductivity data, current density plots with respect to anodic aluminum dissolution, half-cell C-rate capability of mixtures with the additives used in research article as well as the SEM images and EDX data of the full-cell with the electrolyte selected and controlled

Structure–Property Relationship of Polymerized Ionic Liquids for Solid-State Electrolyte Membranes

Eight new polymerized ammonium‐based ionic liquids were prepared as thin membrane films and evaluated within the scope of their usage in lithium‐ion batteries. The focus of this work is to get a better understanding of the influence of structural modifications of the monomers on the polymerized materials. Further, different concentrations of a lithium‐ion conducting salt were applied in order to receive an optimized combination of monomer structure and lithium salt concentration. It was found that an increased side chain length of the studied ammonium‐based polymerized ionic liquids leads to a reduction in glass transition temperatures and increased ionic conductivity values. As a result of the addition of conducting salt to the PIL membranes, the glass transition temperatures and the ionic conductivity values decreases. Nevertheless, PFG‐NMR reveals a higher lithium‐ion mobility for a sample with higher conducting salt content

Poly(ionic liquid) Based Composite Electrolytes for Lithium Ion Batteries

Polymerized ionic liquids (PIL) are an interesting substance class, which is discussed to transfer the outstanding properties and tunability of ionic liquids into a solid material. In this study we extend our previous research on ammonium based PIL and discuss the influence of additives and their usability as polymer electrolyte membranes for lithium ion batteries. The polymer electrolyte is thereby used as replacement for the commercially widespread system of a separator that is soaked with liquid electrolyte. The influence of the material composition on the ionic conductivity (via electrochemical impedance spectroscopy) and the diffusion coefficients (via pulsed-field-gradient nuclear magnetic resonance spectroscopy) were studied and cell tests with adapted membrane materials were performed. High amounts of the additional ionic liquid (IL) MPPyrr-TFSI (1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide) increased the ionic conductivity of the materials up to 1.3·10−4 S·cm−1 but made the usage of a cross-linker necessary to obtain mechanically stable membranes. The application of liquid electrolyte mixtures with ethylene carbonate (EC) and MPPyrr-TFSI decreased ionic conductivity values down to the 10−9 S·cm−1 range, but increased 7Li diffusion coefficients with increasing amounts of EC up to 1.7·10−10 m2·s−1. Cell tests with two membrane mixtures proofed that it is possible to build electrolyte membranes on basis of the polymerized ionic liquids, but also showed that further research is necessary to ensure stable and efficient cell cycling

A framework for service quality assurance using event correlation techniques

Due to the increasing use of service level agreements for the provisioning of IT services, providers have to ensure that the guarantees for the quality of their offered services, expressed by quality of service parameters, are met. These guarantees are endangered by resource malfunctions in the provider’s infrastructure or quality degradations of services which are supplied by subproviders. To optimize the resolution of customer reports about service quality degradations affecting the quality guarantees we propose to apply event correlation techniques. In this paper we present a framework for this new kind of event correlation which is called service-oriented event correlation. The framework bridges the gap between the management of the infrastructure and the offer of services for the customers with respect to the service fault diagnosis. The application of event correlation approaches in the framework is examined in detail.

Lithium-ion Cell Safety Improve by Reduced Pressure

Electrolytes are one of the key components in lithium ion batteries because of their interaction with all materials inside the lithium cell. Usually, they consist of mixtures of organic carbonates as solvents, lithium containing conducting salts, and various additives. During a thermal runaway accident, the electrolyte is one of the most critical compounds due to its potential to form highly toxic and flammable decomposition products. A thermal runaway accident can arise due to various cell failures and usually happens in several steps. In dependence of the cause of the cell failure, different mechanisms led to a worst-case scenario in which the cell becomes un-controllable and a fire accident takes place, as can be observed in the current Li-ion safety problematic. In the process, various gases can be formed at elevated temperatures and will cause a cell bloat and in the end an ignition of the whole cell. During a thermal runaway, the initial “electrolyte burn” will ignite also high-energy electrode material and cause a more pronounced accident. Such a fire can release lots of toxic gaseous electrode metals (Ni, Co, Mn) and fluorine-rich compounds. Thus, not only the fire accident must be brought under control but also the toxic combustion products have to be considered. In this study we developed an approach for preventing Li-ion cell explosions and burns by using reduced pressure. It is demonstrated in proof-of-concept experiments that it is possible by using a vacuum pump as well as a suction unit to prevent a cell explosion successfully. A vacuum pump is often used in the lab to produce a reduced pressure, but such an advice is expensive and unpractical for various applications. Therefore, a suction unit which is much more appropriate in products and applications is also investigated in the study. It is shown that reduced pressure can be used during a thermal runaway accident on cell level to enhance the safety of the unit significantly. Within a thermal runaway a strong temperature increase happens, but the Li-ion cells remain tightly closed. Additionally we present a model how this approach could be used in larger cells and battery packs. Such a control would be advantageous in particular when the battery pack is located in a sensitive area or is used under risky conditions

Investigation of ternary mixtures containing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)azanide, ethylene carbonate and lithium bis(trifluoromethanesulfonyl)azanide

Temperature-dependent viscosity, conductivity and density data of ternary mixtures containing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)azanide (EMIM-TFSA), ethylene carbonate (EC), and lithium bis(trifluoromethanesulfonyl)azanide (Li-TFSA) were determined at atmospheric pressure in the temperature range of 20 to 80 °C. Differential scanning calorimetry (DSC) measurements were performed to characterize phase conditions of the mixtures in a temperature range of −120 to +100 °C. The viscosity data were fitted according to the Vogel-Fulcher-Tammann-Hesse (VFTH) equation and analyzed with the help of the fractional Walden rule. In this study, fundamental physicochemical data about the mixtures are provided and discussed as a basis for structure-property relationship calculations and for potential use of those mixtures as electrolytes for various applications